I tried to post in the chemical forum but it would not let me post, I have no idea where this should be but here it goes:

I have read on here that vinyl lined pools do not require calcium but the pool store guy said that they were sending it to be added to the water "to keep things from rusting". Is that things on the exterior for when the water splashes out. The pool is a swim and play, Islamorada model and it is a steel frame (walls) that have been coated and sealed. Should I have this chemical put in the pool or do I tell them no? The only other information I have on the chemicals is that they are all made by OREQ. Thank you so much for any and all assistance!!